Month: August 2016

“If it wasn’t for the plants, and if it wasn’t for the invertebrates, our ancestors’ invasion of land could never have happened. There would have been no food on land. There would have been no ecosystems for them to populate. So really the whole ecosystem that Tiktaalik and its cousins were moving into back in the Devonian was a new ecosystem. … This didn’t exist a hundred million years before – shallow fresh water streams with soils that are stabilized by roots. Why? Because it took plants to do that – to make the [habitats] in the first place. So really plants, and the invertebrates that followed them, made the habitats that allowed our distant relatives to make the transition from life on water to life on land.” – Neil Shubin, author of Your Inner Fish, in an interview with Cara Santa Maria on episode 107 of her podcast, Talk Nerdy To Me

Plants were not the first living beings to colonize land – microorganisms have been terrestrial for what could be as long as 3.5 billion years, and lichens first formed on rocks somewhere between 550 and 635 million years ago – however, following in the footsteps of these other organisms, land plants paved the way for all other forms of terrestrial life as they migrated out of the waters and onto dry land.

The botanical invasion of land was a few billion years in the making and is worth a post of its own. What’s important to note at this point, is that the world was a much different place back then. For one, there was very little free oxygen. Today’s atmosphere is 21% oxygen; the first land plants emerged around 470 million years ago to an atmosphere that was composed of a mere 4% oxygen. Comparatively, the atmosphere back then was very carbon rich. Early plants radiated into numerous forms and spread across the land and, through processes like photosynthesis and carbon sequestration, helped to dramatically increase oxygen levels. A recent studyfound that early bryophytes played a major role in this process. The authors of this study state, “the progressive oxygenation of the Earth’s atmosphere was pivotal to the evolution of life.”

A recreation of a Cooksonia species – one of many early land plants (photo credit: wikimedia commons)

The first land plants looked very different compared to the plants we are used to seeing today. Over the next few hundred million years plants developed new features as they adapted to life on land and to ever-changing conditions. Roots provided stability and access to water and nutrients. Vascular tissues helped transport water and nutrients to various plant parts. Woody stems helped plants reach new heights. Seeds offered an alternative means of preserving and disseminating progeny. Flowers – by partnering with animal life – provided a means of producing seeds without having to rely on wind, water, or gravity. And that’s just scratching the surface. Rooted in place and barely moving, if at all, plants appear inanimate and inactive, but it turns out they have a lot going on.

But what is a plant again? In part one and two, we listed three major features all plants have in common – multicellularity, cell walls composed of cellulose, and the ability to photosynthesize – and we discussed how being an autotroph (self-feeder/producer) sets plants apart from heterotrophs (consumers). Joseph Armstrong writes in his book, How the Earth Turned Green, “photosynthetic producers occupy the bottom rung of communities.” In other words, “all modern ecosystems rely upon autotrophic producers to capture energy and form the first step of a food chain because heterotrophs require pre-made organic molecules for energy and raw materials.”

So, why should we care about plants? Because if it wasn’t for them, there wouldn’t be much life on this planet to speak of, including ourselves.

Plants don’t just provide food though. They provide habitat as well. Plus they play major roles in the cycling of many different “nutrients,” including nitrogen, phosphorous, carbon, sulfur, etc. They are also a major feature in the water cycle. It is nearly impossible to list the countless, specific ways in which plants help support life on this planet, and so I offer two examples: moss and dead trees.

The diminutive stature of mosses may give one the impression that they are inconsequential and of little use. Not so. In her book, Gathering Moss, Robin Wall Kimmerer describes how mosses support diverse life forms:

There is a positive feedback loop created between mosses and humidity. The more mosses there are, the greater the humidity. More humidity leads inexorably to more mosses. The continual exhalation of mosses gives the temperate rain forest much of its essential character, from bird song to banana slugs. … Without mosses, there would be fewer insects and stepwise up the food chain, a deficit of thrushes.

Mosses are home to numerous invertebrate species. For many insects, mosses are a place to deposit their eggs and, consequentially, a place for their larvae to mature into adults. Banana slugs traverse the moss feeding on “the many inhabitants of a moss turf, and on the moss itself.” In the process they help to disperse the moss.

Moss is used as a nesting material by various species of birds, as well as squirrels, chipmunks, voles, bears, and other animals. Patches of moss can also function as “nurseries for infant trees.” In some instances, mosses inhibit seed germination, but they can also help protect seeds from drying out or being eaten. Kimmerer writes, “a seed falling on a bed of moss finds itself safely nestled among leafy shoots which can hold water longer than the bare soil and give it a head start on life.”

Virtually all plants, from the tiniest tufts of grass to the tallest, towering trees have similar stories to tell about their interactions with other living things. Some have many more interactions than others, but all are “used” in some way. And even after they die, plants continue to interact with other organisms, as is the case with standing dead trees (a.k.a. snags).

In his book, Welcome to Subirdia, John Marzluff explains that when “hole creators” use dead and dying trees, they benefit a host of “hole users:”

Woodpeckers are natural engineers whose abandoned nest and roost cavities facilitate a great diversity of life, including birds, mammals, invertebrates, and many fungi, moss, and lichens. Without woodpeckers, birds such as chickadees and tits, swallows and martins, bluebirds, some flycatchers, nuthatches, wood ducks, hooded mergansers, and small owls would be homeless.

As plants die, they continue to provide food and habitat to a variety of other organisms. Eventually they are broken down to their most rudimentary components, and their nutrients are taken up and used by “new life.” Marzluff elaborates on this process:

Much of the ecological web exists out of sight – underground and in rotting wood. There, molds, bacteria, fungi, and a world of invertebrates convert the last molecules of sun-derived plant sugar to new life. These organisms are technically ‘decomposers,’ but functionally they are among the greatest of creators. Their bodies and chemical waste products provide us with an essential ecological service: soil, the foundation of terrestrial life.

Around 470 million years ago, plants found their way to land. Since then life of all kinds have made land their home. Plants helped lead the way. Today, plants continue their long tradition of supporting the living, both in life and in death.

This is a revised version of a postthat was originally published on January 14th, 2015. It includes excerpts from a chapter entitled, “Portrait of Splachnum,” in the book, Gathering Moss, by Robin Wall Kimmerer.

Certain plants, like corpse flowersand carrion flowers, emit foul odors when they bloom. The scent is akin to the smell of rotting flesh, hence their common names. The purpose of this repugnant act is to attract a specific group of pollinators: flies, carrion beetles, and other insects that are attracted to gross things. Though this particular strategy is rare, these aren’t the only plants that employ stinky smells to recruit such insects to aid in reproduction and dissemination. Consider dung mosses.

No moss is more fastidious in its choice of habitats than Splachnum. Absent from the usual mossy haunts, Splachnum is found only in bogs. Not among the commoners like Sphagnum that build the peaty hummocks, not along the margins of the blackwater pools. Splachnum ampullaceum occurs in one, and only one, place in the bog. On deer droppings. On white-tailed deer droppings. On white-tailed deer droppings which have lain on the peat for four weeks. In July.

At least three genera (Splachnum, Tetraplodon, and Tayloria) in the family Splachnaceae include species that go by the common name, dung moss. All Splachnum and Tetraplodon species and many species in the genus Tayloria are entomophilous. Entomophily is a pollination strategy in which pollen or spores are distributed by insects. Compare this to anemophily, or wind pollination, which is the common way that moss spores are distributed. In fact, dung mosses are the only mosses known to exhibit entomophily.

Before we go too much further, it’s important to understand how mosses differ from other plants. Mosses are in a group of non-vascular and non-flowering plants called bryophytes. Vascular tissues are the means by which water and nutrients are transported to and from plant parts. Lacking vascular tissues, water and nutrients are simply absorbed through the leaves and stems of mosses, which is why mosses are typically petite and prefer moist environments. Mosses also lack true roots and instead have rhizoids – threadlike structures that anchor the plants to their substrate of choice (such as dung).

Another major distinction between bryophytes and other plants is that bryophytes spend most of their life cycle as a haploid gametophyte rather than a diploid sporophyte. In most plants, the haploid gametophytes are the sperm (pollen) and egg cells; the sporophyte is everything else. In mosses, the familiar green, leafy structure is actually the gametophyte. The gametophyte houses sperm and egg cells, and when the egg is fertilized by sperm it forms a zygote that develops into the sporophyte structure which extends above the leafy gametophyte. A capsule at the top of the sporophyte contains spores which are eventually released and, upon finding themselves on a suitable substrate in a hospitable environment, germinate to produce new plants. The spore then is comparable to a seed in vascular, seed-bearing plants.

As stated earlier, the spores of most mosses are distributed by wind. Dung mosses, on the other hand, employ flies in the distribution of their spores. They attract the flies by emitting scents that only flies can love from an area on the capsule of the sporophyte called the apophysis. This area is often enlarged and brightly colored in yellow, magenta, or red, giving it a flower-like appearance which acts as a visual attractant. The smells emitted vary depending on the type of substrate a particular species of dung moss inhabits. Some dung mosses grow on the dung of herbivores and others on the dung of carnivores. Some even prefer the dung of a particular group of animals; for example, a population of Tetraplodon fuegiensis was found to be restricted to the feces and remains of foxes. However, dung is not the only material that dung mosses call home. Certain species grow on rotting flesh, skeletal remains, or antlers.

Splachnum ampullaceum inhabits the droppings of white-tailed deer. Had a wolf or coyote followed the scent of the deer into the bog, its droppings would been colonized by S. luteum. The chemistry of carnivore dung is sufficiently distinct from that of herbivores to support a different species. … Moose droppings have their own loyal follower. The family to which Splachnum belongs includes several other mosses with an affinity for animal nitrogen. Tetraplodon and Tayloria can be found on humus, but primarily inhabit animal remains such as bones and owl pellets. I once found an elk skull lying beneath a stand of pines, with the jawbone tufted with Tetraplodon.

Yellow moosedung moss (Splachnum luteum) has one of the largest and showiest sporophytes. (photo credit: www.eol.org)

The set of circumstances that converge to bring Splachnum into the world is highly improbable. Ripening cranberries draw the doe to the bog. She stands and grazes with ears alert, flirting with the risk of coyotes. Minutes after she has paused, the droppings continue to steam. … The droppings send out an invitation written in wafting molecules of ammonia and butyric acid. Beetles and bees are oblivious to this signal, and go on about their work. But all over the bog, flies give up their meandering flights and antennae quiver in recognition. Flies cluster on the fresh droppings and lap up the salty fluids that are beginning to crystallize on the surface of the pellets. Gravid females probe the dung and insert glistening white eggs down into the warmth. Their bristles leave behind traces from their earlier foraging trips among the day’s dung, delivering spores of Splachnum on their footprints.

The spores of dung mosses are small and sticky. When a fly visits these plants, the spores adhere to its body in clumps. The fly then moves on to its substrate of choice to lay its eggs, and the spores are deposited where they can germinate and grow into new moss plants. Flies that visit dung mosses receive nothing in return for doing so, but instead are simply “tricked” into disseminating the propagules. The story is similar with corpse flowers and carrion flowers; flies are drawn in by the smells and recruited to transmit pollen while receiving no nectar reward for their work.

There are 73 species in the Splachnaceae family, and nearly half of these species are dung mosses. Most are found in temperate habitats in both the northern and southern hemispheres, with a few species occurring in the mountains of subtropical regions. They can be found in both wet and relatively dry habitats. Dung mosses are generally fast growing but short lived, with some lasting only about 2 years. It isn’t entirely clear how and why mosses in this family evolved to become entomophilous, but one major benefit of being this way is that their spores are reliably deposited on suitable habitat.

Since Splachnum can grow only on droppings, and nowhere else, the wind cannot be trusted with dispersal. Escape of the spores is successful only if they have both a means of travel and a reserved ticket for a particular destination. In the monotonous green of the bog, flies are attracted to the cotton candy colors of Splachnum, mistaking them for flowers. Rooting about in the moss for non-existent nectar the flies become coated with the sticky spores. When the scent of fresh deer droppings arrives on the breeze, the flies seek it out and leave Splachnum-coated footprints in the steaming dung.

Major outbreaks of grasshoppers can be devastating. A plague of locusts of biblical proportions can decimate crop fields and rangelands in short order. Clouds of grasshoppers moving in and devouring every plant in sight makes it easy to see why these insects are often seen as pests. Even small groups of them can do significant damage to a garden or farm. Yet, grasshoppers and their relatives have great ecological value and are important parts of healthy ecosystems. Love them or hate them, they are an essential piece of a bigger picture.

Grasshoppers are in the order Orthoptera, an order that includes katydids, crickets, wetas, and a few other familiar and not so familiar insects. Worldwide, there are more than 27,000 species of orthopterans. These insects mostly feed on plants; many are omnivorous while others are exclusively herbivorous. They are most commonly found in open, sunny, dry habitats like pastures, meadows, disturbed sites, open woods, prairies, and crop fields. Most insects in this order are fairly large, making them easy to identify; yet they don’t seem to receive the same level of human attention that charismatic insects like bees and butterflies do. In Field Guide to Grasshoppers, Katydids, and Crickets of the United States, the authors defend this diverse group of arthropods: “Grasshoppers often are thought of as modest-looking brown or green insects, but many species in this family are brightly colored, and some of the most dull-colored species rival butterflies in beauty when they spread their wings in flight.”

The voracious appetite of grasshoppers and their preference for plants can influence ecosystems in many ways. Certain plants may be favored over others, which affects the diversity and distribution of plant communities. Grasses are a particular favorite, despite being high in hard to digest compounds like lignin, cellulose, and silica. As grasshoppers consume vegetation – up to their body weight per day – digested materials return to the soil where soil dwelling organisms continue to break them down. In this way, grasshoppers and their relatives are major contributors to nutrient cycling. Returning nutrients to the soil results in increased nutrient availability for future plant growth. In fact, one grassland study found that despite short-term losses via grasshopper herbivory, plant growth was enhanced in the long-term due in part to accelerated nutrient cycling.

Because grasshoppers are such prolific consumers, their robust bodies are loaded with nutritious proteins and fats, making them a preferred food source for higher animals. Reptiles, raccoons, skunks, foxes, mice, and numerous species of birds regularly consume grasshoppers and related species. While many adult birds feed mostly on seeds and fruits, they seek out insects and worms to feed their young. Nutrient-packed grasshoppers are an excellent food source for developing birds. Humans in many parts of the world also find grasshoppers and crickets to be a tasty part of their diet.

Grasshoppers provide food for other invertebrates as well. The aforementioned field guide refers to the fate of grasshoppers and certain species of blister beetles as being “intimately linked,” because the larvae of these blister beetles feed exclusively on grasshopper eggs. Several species of flies and other insects, as well as spiders, also feed on grasshoppers and other orthopterans.

In short, grasshoppers play prominent roles in plant community composition, soil nutrient cycling, and the food chain. When grasshopper populations reach plague proportions, their impact is felt in other ways. From a human perspective, the damage is largely economic. However, their ability to thoroughly remove vegetation across large areas can be environmentally devastating as well, particularly when it comes to soil erosion and storm water runoff. The USDA’s Agricultural Research Service considers grasshoppers “among the most economically important pests” and cites research estimating that they are responsible for destroying as much as 23% of available range forage in the western United States annually. A paper published in the journal, Psyche, references a period between 2003-2005 in Africa where locusts were responsible for farmers losing as much as 80 to 100% of their crops.

This level of devastation is relatively rare. In Garden Insects of North America, Whitney Cranshaw states that of the more than 550 species of grasshoppers that occur in North America, “only a small number regularly damage gardens…almost all of these are in the genus Melanoplus.” Like most large, diverse groups of organisms, many grasshopper species are abundant and thriving while others are rare and threatened. Human activity has benefited certain species of grasshoppers while jeopardizing others. In general, grasshopper populations vary wildly from year to year depending on a slew of environmental factors.

Differential grasshopper (Melanoplus differentialis) – one of the four grasshoppers that Whitney Cranshaw lists as “particularly injurious” in his book Garden Insects of North America. (photo credit: www.eol.org)

A plague or outbreak of grasshoppers is a poorly understood phenomenon. It seems there are too many factors at play to pin such an occasion on any one thing. Warm, sunny, dry weather seems to favor grasshopper growth and reproduction, so drought conditions over a period of years can result in a dramatic increase in grasshopper populations. But drought can also limit plant growth, reducing the grasshoppers’ food supply. Natural enemies – which grasshoppers have many – also come into play. It seems that just the right conditions have to be met for an outbreak to occur – a seemingly unlikely scenario, but one that occurs frequently enough to cause concern.

Grasshoppers and fellow orthopterans are fascinating insects, and their place in the world is worth further consideration. For an example of just how compelling such insects can be, here is a story about crickets from Doug Tallamy’s book, Bringing Nature Home:

“Male tree crickets in the genus Oecanthus attempt to lure females to them by making chirping songs with their wings. The loudest male attracts the most females, so males often cheat a bit by positioning themselves within a cup-shaped leaf that amplifies the song beyond what the male can make without acoustical help. Each male chews a hole in the center of his cupped leaf that is just large enough to accommodate his raised wings during chirping. This ensures that the sound projects directly from the center of the parabolic leaf for maximum amplification.

As the human population balloons and cities sprawl, ecological studies in urban areas are following suit. Nature has always been a component of cities – we can’t escape it after all, as hard as we may try – but urban nature (and the enhancement of it) has become increasingly important as the human species continues to urbanize. More and more we are seeing the importance of melding the built environment with the natural one. Our motivations are diverse – albeit largely anthropocentric. But that’s fine. As we make improvements to the live-ability of cities for human’s sake, other living beings benefit. We are finding ways to get along with our neighbors, and we are learning to appreciate and value them as well.

Since 2008, the world’s urban population has outnumbered its rural population, and it is predicted that by 2050, more than two-thirds of humans will be urbanites. Immense resources are required to support such large, concentrated populations, and most of these resources are produced outside of urban areas. This results in an ecological footprint that is significantly larger than the city itself. Additionally, waste and pollution produced within cities negatively effects surrounding areas and beyond in abundant ways.

In May of this year, Science put out a special issue entitled, “Urban Planet,” which features a series of articles that address some of the latest research in urban ecology and discuss current developments and future research needs – a sort of state of the union address for urban ecology in 2016. A series of 13 articles covered diverse topics including city-integrated renewable energy, innovative solutions to water challenges, transportation and air pollution, and food security in an urban world. Rodent-borne diseases in urban slums, creating sustainable cities in China, and Vancouver’s push to become the “greenest city” were also features of this special issue.

The issue serves to highlight the importance of this field of study and the urgency there is in finding solutions to major environmental challenges. But it also offers hope. Bright minds are working towards solutions to this century’s biggest problems as we look towards a more sustainable future. The introduction emphasizes that “the rise of cities is not…all doom and gloom.” Urbanization has upsides: “consolidating human populations helps shrink our individual environmental footprints, and cities are serving as living laboratories for further improvements.”

Urban ecology is a relatively recent subfield of ecology. In The Ecological Future of Cities, Mark McDonnell and Ian MacGregor-Fors describe how it “arose in the 1990’s out of a need to increase our…understanding of the ecological and human dimensions of urban ecosystems.” Initially the field was mainly concerned with biodiversity and the ecosystem processes and services found within cities. Findings from these studies are now influencing urban planning, design, and management. Such decisions are also informed by more recent studies in the field of urban ecology, which has grown to include “issues of sustainability, environmental quality, and human well-being in urban ecosystems.”

The authors note that our ecological understanding of cities was waylaid because “nature within cites was long considered unworthy of study, except when it involved solving environmental problems that threatened human well-being.” Cities were perceived as unnatural because humans had “disrupt[ed] the natural ecological conditions and processes that scientists [were] attempting to understand.” Today, ecologists recognize that studies in the field of urban ecology help us better understand basic ecological principles, while also providing “valuable information for creating liveable, healthy, and resilient urban environments.”

Studies in urban ecology have also increased our understanding of the mechanisms involved in evolution and adaptation. To illustrate this, the authors offer examples of birds that modified their songs “to communicate at noisy locations” and plants that shifted their seed dispersal strategies to survive in “highly fragmented urban habitats.” The authors also highlight the importance of maintaining or restoring natural vegetation in urban areas in order to help preserve struggling species of plants and animals, citing a study that found that “fewer local plant extinctions occurred in cities that maintained at least 30% native vegetation cover.” Additionally, the authors note that “the scope of urban ecology research extends well beyond city limits,” since urbanization is partly to blame for numerous environmental issues including habitat loss and fragmentation, biodiversity loss, climate change, and invasive species.

In Living in Cities, Naturally, Terry Hartig and Peter Kahn, Jr. address the topic of mental health and urban living. While there is still much to learn about the relationship between the two, it is generally believed that viewing or spending time in nature can help improve one’s mental well-being. As the authors put it, “parks and green spaces” can be viewed as “health resources for urban populations,” and including natural areas and natural processes in the design and creation of cities is necessary “for psychological as well as ecological purposes.”

Interacting with nature in an urban setting can help people develop positive feelings about the natural world and may encourage support for environmental protection. The authors worry that if future generations grow up without an intimate connection to the natural world, elevated amounts of environmental degradation will be seen as normal and a feeling of urgency to protect the environment from continued degradation will fade. This is why including plentiful amounts of green space within cities is essential: “Providing opportunities for people to experience more robust, healthy, and even wilder forms of nature in cities offers an important solution to this collective loss of memory and can counter the shifting baseline.”

This special issue of Sciencehighlights some of the current ecological and environmental research regarding urbanization. For a great introductory look at urban ecology and basic ecological principles, check out the book, Nature All Around Us. Also, expect to see many more urban ecology themed posts on Awkward Botany. Tell your friends.

Occasionally I receive packets of wildflower seeds from companies that are not in the business of growing plants. They are promotional items – encouraging people to plant flowers while simultaneously marketing their wares. Often the seed packet lacks a list of the seeds included in the mix, and so it remains unclear what “wildflowers” are actually in there. My guess is that most seed packets like this go unplanted, and those that do get planted, may go uncared for. After all, the company that supplied them isn’t all that concerned about what gets done with them anyway.

As it is, generic packets of wildflower seeds like this may not actually contain any wildflower seeds. The term wildflower generally refers to a flowering plant that grows in the wild and was not intentionally planted by humans. It is synonymous with native plant, but it can also refer to non-native plants that have become naturalized. By this definition, a packet of wildflower seeds should only include seeds of native or naturalized plants and should not include horticultural selections, hybrids, or cultivated varieties. Ideally, the seed mix would be specific to a particular region, as each region throughout the world has its own suite of native wildflowers.

With that in my mind, I was immediately curious about an unlabeled packet of wildflower seeds I recently received as a promotional item from a company that has nothing to do with plants. This is a company that ships items nationwide and around the world, which leads me to believe that hundreds of people received similar packets of seeds around the same time I did. The seed packet is not labeled for a particular region, so all of us likely received a similar mix of seeds. “Wildflowers” then, at least in this case, means a random assortment of flowering plants with questionable provenance and no sense of geographic location.

The seed packet in question.

Curiousity is killing me; so I am determined to find out what is in this mysterious packet of seeds. Using a pair of magnifying glasses, I seperated the seeds into 26 groups. Each group, from as best as I can tell, should be a unique species (or at least from the same genus). The next step will be to grow the seeds out and see what they actually are. I have limited space and time, so this is going to take a while. Since “wildflower” is not an exact term, I have decided that in order to be considered a wildflower the plant will have to be native to North America. (I should probably say western North America or Intermountain West, since that is where I am located, but that’s pushing it.)

The amount of seeds that each of the 26 groups consists of varies greatly, from a single seed to 52 seeds. Some of the seeds may not be viable, and some of the seedlings are sure to perish along the way. Despite losses, it should be clear in the end what this packet of seeds mainly consists of and whether or not it is indeed a wildflower seed mix. If I were skilled at identifying species simply by observing their seeds, I might be able to avoid growing them out, but I am not confident enough to do that. However, one group of seeds is almost certainly calendula. Calendula is a genus native to parts of Asia, Europe, and North Africa that has been introduced to North America. So, we’re already off to a bad start.

To be clear, I have no intention of disclosing or calling out the company that sent the seeds. This is all in good fun. No hard feelings. I’m satisfying my own curiosity, and perhaps yours, too. Until the next update (which could be a while), go run through a field of wildflowers. Enjoy yourself.